The present invention relates generally to the field of electrosurgery. More particularly, the present invention relates to a system for controlling heat transfer from surgical electrodes to adjacent tissue.
During the course of surgical procedures it is often necessary to cauterize or coagulate tissue to control bleeding. Electrosurgical devices are known which utilize electrical current for tissue cauterization. U.S. Pat. Nos. 1,983,669 and 4,637,392 disclose electrical cauterization devices in which electrodes are disposed about the surface of a probe. Tissue is heated and coagulation is effected by delivering electrosurgical energy to tissue through the electrodes. Among the drawbacks of such devices is the potential that the electrodes will become overly heated, thus prematurely dessicating the tissue and causing the tissue to stick to the electrodes. This can result in further bleeding upon disengagement of the electrodes from the tissue, and the need to remove tissue from the electrode before continuing to use the device. Moreover, it can be inconvenient to use such cauterization devices during certain surgical procedures because cutting and cauterization must be performed with separate instruments.
Various electrosurgical probes exist for transferring energy to a biological site. Typically these probes dispose a metallic electrode along the outer surface of a rigid shaft. When the probe is positioned within the patient, the probe is in contact with the tissue at the surgical site. As energy is transferred through the electrode, electrical currents are established within adjacent tissue. As current passes through the tissue, some energy is absorbed into the tissue causing tissue temperature to rise. The rising temperature of the tissue denatures tissue protein molecules and facilitates coagulation.
Among the drawbacks of such devices is the potential that the electrodes will become overheated, and the denatured proteins will weld to the electrode on the outer surface of the probe. This can result in tissue searing or dessication, or in tissue being torn from the surgical site as the probe is removed from the patient. Such a tear can result in bleeding or the reopening of a wound. A further problem results from tissue collecting over the probe. Tissue stuck to the probe interferes with the delivery of energy to the surgical site. This interference limits the depth of penetration of energy into the tissue and thereby limits the depth of cauterization. Because of these drawbacks these devices are impractical for certain surgical procedures.
Surgical systems exist that attempt to limit the sticking of tissue to surgical probes. Some thermal cauterizing probes have placed a non-stick coating of TEFLON (a fluorocarbon polymer) around the thermal electrode. However, because teflon does not conduct electricity the use of this technique for electrosurgical probes is impractical. Some electrosurgical systems monitor the temperature of the electrodes at the probe and reduce the energy being transferred to the site in order to control the temperature of the probe. This process results in a fluctuating energy density being delivered to the surgical site and a resulting uncertainty as to the depth of cauterization being effected.
There is a need for an electrosurgical device and system that can perform tissue cutting procedures and tissue cauterization procedures without overheating and causing tissue to stick or weld to the electrode. Such a device would be useful in that it would eliminate the need for the surgeon to scrape tissue and/or coagulant from the probe during the cauterization or cutting procedure. A device of this type would be well suited to general surgical procedures as well as to microsurgical procedures.
Accordingly, it is an object of the present invention to provide a surgical device and system that controls the transfer of heat from the device to tissue at the surgical site. A further object of the invention is to provide such a device that is adapted to control the temperature of an electrode mounted on an electrosurgical device. Yet another object of the invention is to provide an electrosurgical device that controls the transfer of heat from the electrode to adjacent tissue without limiting the electromagnetic energy delivered to the tissue. It is also an object of the invention to provide an electrosurgical device that prevents tissue and/or coagulant from welding to an energy delivering electrode. Other objects of the invention will be apparent upon reading the description which follows.